I think the concept of "Sustained Health" is an interesting one to contemplate.
It's more than just "getting in shape", or "working out." And, it's far more than a "Wellness Program."
When people ask me "Why should I practice yoga?" - my first response is usually "How long do you plan on living in that body?"
Yoga has a positive impact on Sustained Health in 4 ways:
1) Physical - it's one of the very few (if only) activities that balances and re-integrates the entire neuro-muscular-skeletal archtecture back to homeostatis.
2) Emotional - it's an activity that settles the nerves - the neuro-channel-fibers to emotional health
3) Mental - through meditative and conscious breathing, the mind quiets and rests (without falling asleep).
4) Vibratory - (or Spiritual if you like) it heightens one's awareness of inter-connectedness.
Furthermore, yoga has a cummulative effect. Each practice builds upon the previous and a store of health and sustainability is built.
There's really only one challenge to achieving Sustained Health, and that's PRACTICE.